UNITED NATIONS (CNN) -- The government of Sudan and militias have acted together in committing widespread atrocities in Darfur that should be prosecuted by an international war crimes tribunal, but the violent acts do not amount to genocide, a U.N. commission has said.

The commission, charged with investigating the violence that has claimed tens of thousands of lives and displaced more than 1.8 million people, found that "most attacks were deliberately and indiscriminately directed against civilians."

"In particular, the commission found that government forces and militias conducted indiscriminate attacks, including killing of civilians, torture, enforced disappearances, destruction of villages, rape and other forms of sexual violence, pillaging and forced displacement, throughout Darfur," the commission said in its 176-page report.

"These acts were conducted on a widespread and systematic basis, and therefore may amount to crimes against humanity."

However, the commission said it does not believe the atrocities committed amount to a policy of genocide, as the United States has alleged.

"The crucial element of genocidal intent appears to be missing, at least as far as the central government authorities are concerned," the report said.

"Generally speaking, the policy of attacking, killing and forcibly displacing members of some tribes does not evince a specific intent to annihilate, in whole or in part, a group distinguished on racial, ethnic, national or religious grounds."

The commission goes on to say that it recognizes that in some instances, individuals -- including Sudanese government officials -- "may commit acts with genocidal intent."

"Whether this was the case in Darfur, however, is a determination that only a competent court can make on a case-by-case basis," it said.

The commission added: "International offenses such as the crimes against humanity and war crimes that have been committed in Darfur may be no less serious and heinous than genocide."

The commission said it was withholding the names of those behind the violence, but said senior government officials and military commanders may be responsible "for knowingly failing to prevent or repress the perpetration of crimes."

It said the names were being withheld publicly to protect witnesses from retribution, to respect due process and because the commission was not vested with investigative or prosecutorial powers.

"The commission instead will list the names in a sealed file that will be placed in the custody of the U.N. secretary-general," the report said.

It also said the material should be passed on to the prosecutor at the International Criminal Court at The Hague, which prosecutes war crimes and other atrocities.

The report found that Arab Janjaweed militias in Darfur were "acting, under the authority, with the support, complicity or tolerance of the Sudanese State authorities."

The conflict in Darfur began intensifying in 2003, when two non-Arab African groups took up arms against what they believed to be the Arab-dominated government's discrimination against black Africans.

A counterinsurgency campaign ensued, in which the Janjaweed -- a term that literally means "devil on a horse" -- committed atrocities that have devastated the region.

The report found that some recruits for the Janjaweed are fighters from Libya, Chad and other nations.

The report also said Sudan's People's Armed Forces played a key role in the armed conflict, and that the National Security and Intelligence Service had a central role and "is responsible for the design, planning and implementation of policies associated with the conflict."

The commission was formed in October 2004 and its members visited Sudan in November and January of this year. Its investigative team remained in Sudan from November through January.

The commission found that the atrocities continued, even as it met with Sudanese officials.

The United Nations has estimated that more than 70,000 people have died in Sudan, the result of the violence and malnutrition plaguing the area.

But U.N. officials say the number is believed to be much higher than that, because the United Nations has documented deaths only since April 2004.

The conflict has displaced an estimated 1.6 million people within Darfur, with another 200,000 fleeing to neighboring Chad, according to U.N. figures.